Radial stackers have been used for many years to stack bulk materials such as aggregate for road construction, grain and coal. Radial stackers, which swing around in a radius to stack material in an arc, permit substantially more material to be stacked than is possible using a conventional stationary stacker that permits only a conical stack. Telescoping radial stackers permit even more material to be stacked as the stacker is extended or retracted during conveying operations.
Radial stackers typically include a wheels or tracks disposed between a hopper and the top of the stacker from which the material is discharged. These wheels or tracks permit the stacker to be maneuvered around the work site or can be swung in an arc, with the hopper including a pivot plate on which the stacker pivots. Whether wheels or tracks are used, portable radial stackers may be folded over themselves and be ready for road transport in relatively little time. If wheels are used, the wheels can be displaced into a position aligned with the stacker to support the stacker for travel down the highway. In that instance, the same wheels that support the stacker during stacking operations can be used to support the stacker above the road. In the event tracks are used in place of wheels, the stackers are folded over themselves and then typically are driven onto a flatbed truck to be conveyed to the next work site.
In either event, whether a wheeled or track system is utilized, it is critical that, when the conveyor is folded over itself, the profile of the stacker be as low as possible due to highway requirements and the desire to avoid extra fees and trouble for having a high load. However, given that the engine that drives the hydraulic systems for the conveyor is typically disposed above the drive, whether it be wheeled or tracked, this requires the height of the folded conveyor to be higher than if the drive engine, drive pulleys and hydraulic systems were placed somewhere else on the conveyor.
In recent years, tracked drives have been used in quarries, agricultural and mining operations to enable equipment to be moved over harsh terrain for ideal positioning for stacking operations. While tracked vehicles have proven to be of great benefit for such purposes, the use of tracks instead of wheels makes it more difficult to shift a stacker radially to facilitate the stacking of material in an arc instead of a cone. Also, because tracked vehicles are not typically permitted to be driven on road surfaces, they are normally loaded onto flatbed trucks for transit from one work site to another. These two drawbacks with the use of tracks has to a certain extent limited the use of tracked vehicles.